Re: [Xen-devel] [V9 PATCH 4/8] pvh dom0: Add checks and restrictions for p2m_is_foreign

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.04.14 at 02:12, <mukesh.rathor@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/mm/p2m-ept.c
> +++ b/xen/arch/x86/mm/p2m-ept.c
> @@ -657,6 +657,7 @@ static void ept_change_entry_type_global(struct 
> p2m_domain *p2m,
>  
>      BUG_ON(p2m_is_grant(ot) || p2m_is_grant(nt));
>      BUG_ON(ot != nt && (ot == p2m_mmio_direct || nt == p2m_mmio_direct));
> +    BUG_ON(p2m_is_foreign(nt) || (p2m_is_foreign(ot) && 
> !p2m_is_invalid(nt)));

So what would a p2m_foreign -> p2m_invalid (permitted by this)
transition mean?

Also, as I'm about to severely restrict the set of types that can be
passed into this and the corresponding (generic) range functions, do
you have any intended use case for this (making it so you need to
permit that transition)?

Jan


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